Field of the Invention
The invention relates to an interface circuit for transmitting binary signals, having a signal transmitting device, a signal receiving device and a transmission device disposed between them.
Such interface circuits are known in manifold versions, for instance from a book by U. Tietze and C. Schenk, entitled: Electronic Circuits--Design and Applications, Springer-Verlag Berlin, Heidelberg 1991, pp. 608-629. The problem of interference in analog circuit parts occurs very frequently in the transmission of binary signals in conjunction with sensitive analog circuits. Admittedly, the interferences can be reduced by lowering the signal amplitude, but that often makes the interface itself more vulnerable to interference. Reducing the signal amplitude is especially critical whenever the switchover time, for instance from high to low, is to be detected precisely. As a rule, the steepest possible pulses with high amplitude are employed for that purpose, but they have an especially broad signal spectrum and therefore a major interfering effect. Moreover, steep pulses involve the risk of the ascending and descending edges of the binary signals being flattened in different ways by the transmitting device, so that other transmission errors result because of the thus-altered duty cycle.